Piston press

ABSTRACT

A piston press in which hydraulic lines ( 32 ) of a hydraulic cylinder ( 19 ) move a ram plate ( 21 ) up and down with relatively large diameters, and in which use is made of a hydraulic pump ( 33 ) with a continuously adjustable delivery flow, in particular with constant output regulation, making it possible to move the ram plate ( 21 ) more quickly in the unloaded or less loaded state, by which means the operating time is shortened considerably as compared with known piston presses ( 10 ).

STATEMENT OF RELATED APPLICATIONS

[0001] This patent application claims priority under 35 USC 119 on German Patent Application No. 102 38 359.6 filed on 16 Aug. 2002.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The invention relates to piston presses for pressing liquids out of laundry, in particular, comprising a press ram which has a hydraulic cylinder and a ram plate assigned to the hydraulic cylinder or arranged at the free end of a piston rod of the hydraulic cylinder, and comprising a hydraulic pump for supplying at least the hydraulic cylinder of the press ram with hydraulic fluid, and to piston presses for pressing liquids out of laundry, in particular, comprising a press frame which has a base and a press ram which can be moved up and down, and comprising a press basket for holding the laundry.

[0004] 2. Prior Art

[0005] Piston presses of the type addressed here are used for removing liquids from moist or wet goods to be pressed. Such piston presses are preferably used in laundries, in order to dewater laundry of all types. For this purpose, the laundry coming from a washing machine is freed in the piston press from a major part of the liquid still bound in it, what is known as the bound solution. The liquid is pressed out of the laundry under high pressure by the piston press, and the laundry, for the major part freed from the bound solution, is then dried.

[0006] The piston press has a press frame to which a press ram is fixed. The press ram has a hydraulic cylinder and a ram plate which can be moved up and down by the hydraulic cylinder. For this purpose, the ram plate is fixed to the free end of a piston rod which can be moved in and out and belongs to the hydraulic cylinder.

[0007] After the laundry has been dewatered by moving the ram plate downwards, the ram plate of the press ram has to be moved up, unloaded, in an idle stroke. In the process, the hydraulic fluid located on the piston side of the hydraulic cylinder has to flow back into a hydraulic tank. As a result, in the case of known piston presses, the idle stroke for moving the ram plate up requires a great deal of time, which unnecessarily prolongs the cycle time of the dewatering operation.

[0008] In addition, moving the ram plate downwards is also to some extent carried out without any contact between the ram plate and the laundry, that is to say substantially with no load. In order to reduce the time for moving the ram plate downwards with no load, in known piston presses it is known to use hydraulic pumps with two different delivery flows. When the ram plate is moved downwards with no load, the hydraulic cylinder is operated with a higher delivery flow. At the correct time before the laundry is reached, the hydraulic pump is switched over to a low delivery flow, as a result of which the ram plate is lowered at a comparatively low speed until dewatering has been completed. The two-stage lowering speed of the ram plate which is brought about as a result still leads to quite high cycle times of each dewatering operation.

[0009] On the basis of the above, the invention is based on the object of providing a piston press which operates reliably and which has cycle times which are reduced as compared with known piston presses.

BRIEF SUMMARY OF THE INVENTION

[0010] A piston press for achieving this object has the features of a press ram which has a hydraulic cylinder and a ram plate arranged at the free end of a piston rod of the hydraulic cylinder, and comprising a hydraulic pump for supplying at least the hydraulic cylinder of the press ram with hydraulic fluid, characterized in that the hydraulic pump is designed in such a way that its delivery flow can be adjusted continuously. As a result of using a hydraulic pump with continuously adjustable delivery flow, the ram plate of the press ram can always be moved up and down at maximum speed. The speed of travel of the ram plate can in this way be adapted to the conditions prevailing at the time. As a result, the shortest possible cycle times can be implemented. In particular, the ram plate can execute idle strokes for moving up and for being lowered onto the laundry under no load at the greatest possible speed.

[0011] Use is preferably made of a hydraulic pump whose delivery flow can be varied as a function of the loading. In particular, the hydraulic pump is regulated in such a way that its output is approximately constant, by which means, with a lower loading on the press ram, the hydraulic pump produces a higher delivery flow and, as a result, the ram plate is moved up and down more quickly under low loading.

[0012] A further piston press for achieving the object mentioned at the beginning, which can also be an advantageous development of the piston press described previously, has the features of a press ram which has a hydraulic cylinder with a ram plate assigned to the latter, and comprising a hydraulic pump for supplying at least the hydraulic cylinder of the press ram with hydraulic fluid, characterized in the hydraulic lines between the hydraulic cylinder and the hydraulic pump and a tank for hydraulic fluid have a relatively large cross section. To this end, hydraulic lines leading at least to the piston side, preferably also to the piston-rod side, of the hydraulic cylinder, including the connections, are provided with a relatively large cross section. This is a cross section which is larger than the usual, standardized cross section of the connections and the associated hydraulic lines to the respective hydraulic cylinder. As a result, relatively large flow paths are provided for the hydraulic fluid flowing to the hydraulic cylinders and also the hydraulic fluid flowing away. In particular, the hydraulic cylinder for moving the ram plate up and down can be supplied with high volume flows of hydraulic fluid in the unloaded or little loaded state. Above all, the flow cross sections of the hydraulic lines and connections for hydraulic fluid flowing away are designed to be relatively large. In this way, a large quantity of hydraulic fluid can flow away from the hydraulic cylinder. An equally large quantity of hydraulic fluid can be supplied on the other side of the hydraulic cylinder, which means that the ram plate can be moved up and down at high speed by the hydraulic cylinder. Above all, in this way the idle stroke for raising the ram plate into the initial position of the piston press may be shortened considerably. However, lowering the ram plate until the latter is loaded can also be carried out very quickly. This applies in particular when operations are carried out with a hydraulic pump whose delivery flow can be adjusted continuously. The speed when lowering the ram plate decreases continuously, to be specific proportionally to the increase in the pressing force, above all when using a hydraulic pump with a continuously controllable delivery flow but constant output.

[0013] Provision is also made to regulate the temperature of the hydraulic fluid, preferably to keep it constant. As a result, the flow rate of the hydraulic fluid through connections and hydraulic lines is not impaired by any increasing viscosity when the hydraulic fluid is too cold. The temperature of the hydraulic fluid is preferably regulated by means of a thermostatic valve. By means of any heating of the hydraulic fluid which may be required, this ensures that the latter constantly has a specific minimum temperature. If required, the hydraulic fluid can be cooled if it is not to exceed a specific temperature.

[0014] A further piston press for achieving the objects mentioned at the beginning, which can also be a preferred development of the piston presses described previously, has the features of a press frame which has a base and a press ram which can be moved up and down, and comprising a press basket for holding the laundry, characterized in that the base has at least one storage container for the liquid pressed out of the laundry. The fact that the base has at least one storage container for the liquid accumulating as the laundry is pressed means that the space in the base, in particular under the base, can be used. The piston press according to the invention becomes more compact as a result. Separate storage containers can in this way be dispensed with. Above all, the space in the base or under the base provides sufficient space to accommodate an adequate quantity of liquid.

[0015] The storage container is preferably dimensioned to be larger than the liquid accumulating overall during each dewatering operation. The storage container in the base of the piston press preferably accommodates twice the quantity of liquid which accumulates during dewatering of a batch of laundry. As a result, the liquid in the storage container can be stored temporarily if required until it is needed in particular for loading a washing machine, namely for washing in the laundry to be washed. As a result of the relatively high storage capacity of the storage container in the base of the piston press, the operation of the washing machine can be decoupled to the greatest extent from the operation of the piston press. According to a development of the piston press according to the invention, the storage container is preferably constructed as a frame tank in the base. Then, virtually the entire frame of the base of the piston press is available for the storage container for storing accumulating liquid.

[0016] Provision is further made for the frame tank to extend at least in a region of the top wall of the base of the piston press which has through holes for leading away the liquid, in particular water, which accumulates when dewatering the laundry. The water can pass directly from the press basket, in which the laundry to be dewatered is located, into the storage container constructed as a frame tank in the base of the piston press. Any pipelines for carrying the accumulating liquid away can be dispensed with as a result.

[0017] A further piston press for achieving the object mentioned at the beginning, which can also be a development of the piston presses described previously, has the features of a press frame which has a base and a press ram which can be moved up and down, and comprising a press basket for holding the laundry, characterized in that at least one analogue distance measuring device is assigned to the press frame to determine the position of at least the press ram. By means of the analogue distance measurement, the position of the press ram and/or of the press basket can be determined reliably and with sufficient accuracy. However, the analogue distance measurement according to the invention is less susceptible to interference and, above all, cheaper than inductive measuring rods used in known piston presses.

[0018] The respective distance measuring device is preferably assigned to a press yoke of the press frame. This provides a reliable, fixed reference point for the analogue distance measuring device. From this fixed reference point, the analogue distance measuring device determines the distance between the ram plate or the press basket and the ram yoke. In this case, the ram plate itself or a flag-like projection arranged on the press basket serves as a reflector for the signals of the analogue distance measuring device. The distance measuring device itself is in this case simultaneously used as transmitter and receiver.

[0019] The analogue distance measuring device is preferably constructed as an acoustic distance measuring device. This is preferably at least one ultrasound sensor. In accordance with the principle of an “echo sounder”, this determines by means of ultrasound waves the distance of the sensor from a point struck by the ultrasound waves. This point acts as a reflector and is assigned to a defined position of the ram plate or the press basket. The distance of the ram plate from the top plate of the base may be determined from the distance determined. Likewise, in this way it is possible to determine whether the press basket is supported with its underside on the top plate of the base or not.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A preferred exemplary embodiment of the piston press according to the invention will be explained in more detail below using the drawings, in which:

[0021]FIG. 1 shows a schematic side view of the piston press.

[0022]FIG. 2 shows a detailed and enlarged illustration of an upper part of the piston press with a press ram.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The figures show a piston press 10 for dewatering washed laundry 11. For this purpose, the liquid contained in the washed laundry 11, namely what is known as the bound solution, is pressed out to the greatest extent by the piston press 10.

[0024] The piston press 10 has a lower base 12 which, on its top side, has a flat top wall 13. In the top wall 13, drainage holes 14 are arranged in some regions. These are through holes, which are designed to lead liquid, in particular water, through the top wall 13. On the top side of the top wall 13, an upper run of a conveyor which is permeable to liquid, at least in the region of the drainage holes 14, can be arranged, with which the laundry 11 can be transported away from the piston press 10 after dewatering. The conveyor, not shown in the figures, can be constructed in such a way that the upper run can be driven in opposite directions, so that the dewatered laundry 11 can optionally be transported away to different, opposite sides of the piston press 10, for example to different conveyors which can in each case be moved in front of a row of dryers arranged beside one another. Each of the conveyors on opposite sides of the piston press 10, which conveyors are preferably also constructed such that they can be raised and lowered, is used for the optional charging of all the dryers in a row.

[0025] Arranged on the base 12 is a plurality of upright columns 15, preferably four columns. The upper ends of all the columns 15 are connected by a press yoke 16. The base 12, the columns 15 and the press yoke 16 substantially form a rigid press frame 17.

[0026] The press yoke 16 bears a press ram 18, preferably centrally. The press ram 18 is formed by a hydraulic cylinder 19 which is fixed to the press yoke 16 and whose piston rod 20 can be led downwards through the press yoke 16. At the lower end, the piston rod 20 has a ram plate 21 firmly connected to the same. The ram plate 21 is preferably cylindrical and, on the underside, has a cushioning element 22 of an elastically deformable material.

[0027] A press basket 23 corresponds to the ram plate 21. The preferably cylindrical press basket 23 is completely open both on the top side and on the lower side. During the dewatering of the laundry 11, the press basket 23 rests with its open underside on the top wall 13 of the base 12 or on the upper run of the conveyor which at least partly covers the top wall 13 of the base 12. The drainage holes 14 passing through the top wall 13 extend in the manner of a grid at least over the region of the circular press basket 23. The laundry 11 to be dewatered is located in the press basket 23. The press ram 18 with the ram plate 21 can be moved into the press basket 23 from the open top side. In the process, the cushioning element 23 under the ram plate 21 presses on the laundry 11 located in the press basket 23 and in so doing dewaters the latter.

[0028] The press basket 23 can be raised and lowered by preferably two mutually opposite pressure-medium cylinders 24, preferably hydraulic cylinders, of which only one pressure-medium cylinder 24 is shown in the figures for improved clarity. The pressure-medium cylinders 24 are fixed with their piston parts 25 under the press yoke 16. A piston rod 26 which can be moved up and down and belongs to each pressure-medium cylinder 24 is attached to a carrier arm 27 firmly connected to a side wall of the press basket 23. The press basket 23 can be raised by the pressure-medium cylinders 24 to such an extent that the open underside of the press basket 23 is spaced so far away from the top wall 13 of the base 12 that the dewatered laundry 11 can pass out of the press basket 23 and can be transported away out of the region of the piston press 10 by the upper run of the conveyor.

[0029] In the piston press 10 shown here, the press basket 23 is constructed from a plurality of parts. Accordingly, the press basket 23 is composed of a lower press basket part 28 and an upper press basket part 29. The lower press basket part 28 is constructed as a thick-walled cylinder with completely open ends. The lower end of the lower press basket part 28 rests on the top wall 13 of the base 12. In terms of height, the lower press basket part 28 is constructed in such a way that the action of pressing the water out of the laundry 11 by means of the press ram 17 is carried out exclusively in it. The upper press basket part 29 is provided with a jacket element of thin sheet metal. The two opposite ends of the upper press basket part 29 are also completely open. The upper press basket part 29 rests with a lower end on the lower press basket part 28, the internal diameter of the upper press basket part 29 either corresponding to the external diameter of the lower press basket part 28 or being slightly greater. The internal diameter of the lower press basket part 28 and of the upper press basket part 29 are somewhat greater than the external diameter of the ram plate 20 of the press ram 17. The press ram 17 can therefore be moved into and out of the press basket 23 without being forced.

[0030] In the exemplary embodiment shown in FIG. 1, the upper region of the upper press basket part 29 is somewhat larger than the lower part of the upper press basket part 29, in that the upper part of the upper press basket part 29 has a lateral widening on one side, specifically on the left-hand side of FIG. 1. This widening corresponds to a loading chute 30 illustrated only schematically in FIG. 1. Via the loading chute 30, the laundry to be dewatered can be conveyed into the press basket 23 with the press ram 17 moved up. In this case, the upper press basket part 29 serves substantially only to guide the laundry 11, in order that the latter passes specifically into the lower press basket part 28, in which the subsequent dewatering of the laundry 11 exclusively takes place.

[0031] On its piston side 31, the hydraulic cylinder 19 of the press ram 18 can be supplied with hydraulic oil via a hydraulic line 32. A hydraulic pump 33 is used for this purpose. If the hydraulic pump 33 supplies hydraulic oil to the piston side 31 of the hydraulic cylinder 19 via the hydraulic line 32, the piston rod 20 is extended and the ram plate 21 is lowered in order to press water out of the laundry 11. In order to move the ram plate 21 up, the piston-rod side 34 of the hydraulic cylinder 19 is supplied with hydraulic oil by the hydraulic pump 33 via a hydraulic line, not shown. In this case, hydraulic oil on the piston side 31 flows at substantially zero pressure into an oil tank, not shown, via the hydraulic line 32.

[0032] According to the invention, the hydraulic line 32 is provided with a relatively large internal diameter. The connections of the hydraulic line 32 to the hydraulic cylinder 19 are also dimensioned such that they have a relatively large free cross section, which preferably corresponds approximately to the internal diameter of the hydraulic line 32.

[0033] The internal diameter of the hydraulic line 32 and the free flow cross sections of the connections are dimensioned such that they are considerably larger than normal connections and hydraulic lines. The internal diameter of the hydraulic lines 32 and the free flow cross section of the connections is preferably 20 to 40%, in particular 25 to 30%, of the piston diameter of the hydraulic cylinder 19. As a result of these relatively large cross sections, relatively high-volume flows of hydraulic oil can flow to the piston side 31 of the hydraulic cylinder 19 and, in particular, large hydraulic oil volumes per unit time can also flow away when the hydraulic cylinder 19 is retracted in order to move a ram plate 21 up. In this way, in particular idle strokes of the hydraulic cylinder 19, specifically both in order to move the ram plate 21 up and also to move the ram plate 21 down onto the laundry 11, are carried out very quickly in spite of the relatively large hydraulic cylinder 19.

[0034] The piston-rod side 34 of the hydraulic cylinder 19 has a considerably smaller volume on the piston side 31, because of the piston rod 26 which is guided therein and has a relatively large diameter as shown in FIG. 2. For this reason, the hydraulic line (not shown) leading to the piston-rod side 34 and its connections are dimensioned with a smaller internal diameter than the hydraulic line 32. As compared with conventional hydraulic lines which lead to the piston-rod side 34 of hydraulic cylinders, the diameter of the hydraulic line that is not shown on the piston-rod side 34 is likewise designed to be considerably larger, according to the invention.

[0035] The diameter of the hydraulic line leading to the piston-rod side 34 of the hydraulic cylinder 19, including the free flow cross sections of the connections, is preferably 5 to 25%, preferably 8 to 15%, of the piston diameter of the hydraulic cylinder 19. As a result, hydraulic oil can escape quickly from the piston-rod side 34 of the hydraulic cylinder 19 when the hydraulic cylinder 19 with the ram plate 21 is to be moved down onto the laundry 11 in the press basket 23. Likewise, in order to move the press ram 18 up quickly, the piston-rod side 34 of the hydraulic cylinder 19 can be supplied with a relatively high hydraulic oil flow.

[0036] According to the invention, the hydraulic pump 33 is also of special design. The hydraulic pump 33 is one whose hydraulic oil delivery flow can be varied continuously. The hydraulic pump 33 can preferably be regulated in such a way that its output remains constant. As a result, when the press ram is unloaded, the delivery flow, that is to say the quantity of the hydraulic oil flow delivered per unit time by the hydraulic pump 33, will increase and, as a result, the press ram 18 with the ram plate 21 will be moved up and down more quickly. With increasing loading on the piston press 10, specifically when the ram plate 21 is acting on the laundry 11 to be dewatered, the delivery rate of the hydraulic oil per unit time (delivery flow) will be reduced by the constantly regulated output from the hydraulic pump 33 at constant pressure. As a result, the pressing force required for effective dewatering can be exerted on the laundry 11 by the ram plate 21 with the cushioning element 22 fixed underneath it, by the press ram 18 being moved downwards more slowly in order to dewater the laundry 11.

[0037] As a result of the special design of the hydraulic pump 33 with constant output, the speed of travel of the ram plate 21 through the hydraulic cylinder 19 decreases proportionally with increasing loading, while, when the press ram 18 is unloaded, for example in order to move the press ram 18 up into the initial position, a greater delivery flow is available, by which means idle strokes of the press ram 18 both in the upward direction and downwards can be carried out very quickly. The cycle time of the piston press 10 according to the invention is effectively reduced as a result.

[0038] The pressure-medium cylinders 24, likewise designed as hydraulic cylinders, for moving the press basket 23 up and down are preferably also supplied with hydraulic oil by the hydraulic pump 33. However, it is also conceivable to use a separate hydraulic pump for this purpose, this also being in particular a hydraulic pump 33 with a continuously variable delivery flow and a control system which keeps the output constant. In addition, the hydraulic connections, not shown, on the piston side and on the piston-rod side of the pressure-medium cylinders 24 designed as hydraulic cylinders are dimensioned with larger diameters than conventional hydraulic lines, as a result of which, just like the hydraulic cylinder 19, the pressure-medium cylinders 24 for raising and lowering the press basket 23 can be retracted and extended relatively quickly.

[0039] The hydraulic oil for supplying the hydraulic cylinder 19 and, if appropriate, also the pressure-medium cylinders 24 is provided with temperature regulation in accordance with a further proposal of the invention. This ensures that the hydraulic oil which is delivered by the hydraulic pump 33 always has a minimum temperature, that is to say is not colder than envisaged. The regulation of the hydraulic oil temperature is preferably carried out by means of a thermostatic valve. In order that the temperature does not fall below a specific minimum, the thermostatic valve regulates heating of the hydraulic oil, which may possibly become necessary. It is also conceivable to provide regulation of the maximum temperature of the hydraulic oil, in order that overheating of the hydraulic oil is avoided. The thermostatic valve is then used for the purpose of alternately managing heating or cooling of the hydraulic oil if the temperature of the hydraulic oil exceeds a maximum value (cooling) or falls below a minimum value (heating).

[0040] The base 12 of the piston press 10 is also constructed in a special way. For this purpose, the base 12 is configured as a frame tank 35, in which at least one storage container 36 is integrated. The frame tank 35, illustrated schematically in FIG. 1, has a hollow space, which forms the storage container 36, in the region between the columns 15. The hollow space is arranged between the top wall 13 and a bottom wall 37 of the base 12, spaced apart from the former. The storage container 36 is located completely in the region under the drainage hole 14 in the top wall 13. The storage container 36 is provided with supporting sections 38 for reasons of stability. The supporting sections 38 are located between the top wall 13 and the bottom wall 37 and support the two mutually in the manner of a frame. Transversely oriented through holes 39 in the supporting sections 38 make the latter permeable to liquid so that, in spite of the supporting profiles 38, a coherent storage container 36 is located under the drainage hole 14 in the top wall 13. If necessary, it is conceivable to design some of the supporting sections 38 to be impermeable to water, so that a plurality of small storage containers 36 are produced, which can be filled and emptied as required. The individual storage containers 36 can be connected to one another by means of pipelines and/or valves in such a way that, if required, an interchange of liquid between the individual storage containers 36 can take place.

[0041] A further special feature of the piston press 10 according to the invention is that the instantaneous position of the press ram 18, in particular of the ram plate 21, is determined continuously by an analogue distance measuring device. In the piston press 10 shown here, the position of the press basket 23 is determined continuously in the same way. The analogue distance measuring device has an acoustic sensor element which, in the exemplary embodiment shown, is designed as an ultrasound sensor 40. The latter is mounted in a fixed position under the press yoke 16, specifically in such a way that an acoustic measuring signal, namely sound waves sent out by the ultrasound sensor 40, strikes an upper side of the ram plate 21. The sound waves are reflected here and received again by the ultrasound sensor 40. By means of measuring the propagation time of the sound waves, the distance of the upper side of the ram plate 21 from the ultrasound sensor 40 on the underside of the press yoke 16 is determined continuously. From this, on the basis of the known constructional dimensions of the piston press 10, the distance of the underside of the ram plate 21 and of the cushioning element 22 fixed underneath it from the press basket 23, in particular the top wall 13 of the base 12, on which the press basket 23 rests, can be determined. Alternatively or additionally, it is also conceivable to provide an ultrasound sensor 40 under the press yoke 16 or on the underside of the ram plate 21, with which the distance of the ram plate 21 and of the cushioning element 22 from the upper side of the heap of laundry 11 in the press basket 23 can be determined. The press ram 18 can then be moved as far as the laundry 11 in a specific manner and at high speed.

[0042] At least one further ultrasound sensor or another acoustic distance measuring device is mounted on the underside of the press yoke 16 in order to determine the position of the press basket 23. This ultrasound sensor is mounted under the press yoke 16 in such a way that its signal, specifically its sound waves, either strikes the carrier arm 27 on the press basket 23 or a separate reflecting means projecting outwards with respect to the press basket 23. By using the sound waves reflected back, the distance of the carrier arm 27 or of the separate reflector on the press basket 23 from the ultrasound sensor on the underside of the press yoke 16 can then be determined. By means of this ultrasound sensor, it is thus possible to establish whether the press basket 23 is standing on the top wall 13 of the base 12 and can be filled with laundry 11 to be dewatered.

List of Reference Symbols

[0043]10 Piston press

[0044]11 Laundry

[0045]12 Base

[0046]13 Top wall

[0047]14 Drainage hole

[0048]15 Column

[0049]16 Press yoke

[0050]17 Press frame

[0051]18 Press ram

[0052]19 Hydraulic cylinder

[0053]20 Piston rod

[0054]21 Ram plate

[0055]22 Cushioning element

[0056]23 Press basket

[0057]24 Pressure-medium cylinder

[0058]25 Piston part

[0059]26 Piston rod

[0060]27 Carrier arm

[0061]28 Press basket lower part

[0062]29 Press basket upper part

[0063]30 Loading chute

[0064]31 Piston side

[0065]32 Hydraulic line

[0066]33 Hydraulic pump

[0067]34 Piston-rod side

[0068]35 Frame tank

[0069]36 Storage container

[0070]37 Bottom wall

[0071]38 Supporting section

[0072]39 Through hole

[0073]40 Ultrasound sensor 

What is claimed is:
 1. Piston press for pressing liquids out of laundry (11) comprising a press ram (18) which has a hydraulic cylinder (19) and a ram plate (21) arranged at the free end of a piston rod (20) of the hydraulic cylinder (19), and a hydraulic pump (33) for supplying at least the hydraulic cylinder (19) of the press ram (18) with hydraulic fluid, characterized in that the hydraulic pump (33) is designed in such a way that its delivery flow can be adjusted continuously.
 2. Piston press according to claim 1, characterized in that the delivery flow of the hydraulic pump (33) can be adjusted as a function of the loading on the hydraulic cylinder (19) or the ram plate (21).
 3. Piston press according to claim 1, characterized in that the delivery flow of the hydraulic pump (33) is regulated as a function of the output.
 4. Piston press according to claim 3, characterized in that the delivery flow of the hydraulic pump can be regulated in such a way that the output of the hydraulic pump (33) is always approximately constant.
 5. Piston press for pressing liquids out of laundry (11) comprising a press ram (18) which has a hydraulic cylinder (19) with a ram plate (21) assigned to the latter, and a hydraulic pump (33) for supplying at least the hydraulic cylinder (19) of the press ram (18) with hydraulic fluid, characterized in the hydraulic lines (32) between the hydraulic cylinder (19) and the hydraulic pump (33) and a tank for hydraulic fluid have a relatively large cross section.
 6. Piston press according to claim 5, characterized in that the diameter of the hydraulic lines (32), including the hydraulic connections, is greater, as compared with the piston diameter of the hydraulic cylinder (19), then the usual standardized diameter of the hydraulic lines (32) and their connections.
 7. Piston press according to claim 5, characterized in that the free flow cross section at least of the hydraulic lines (32) is at least {fraction (1/15)} of the piston diameter of the hydraulic cylinder (19).
 8. Piston press according to claim 5, characterized in that the diameter of the hydraulic line (32) on the piston side (31) is at least ⅕ of the piston diameter of the hydraulic cylinder (19).
 9. Piston press according to claim 5, characterized in that the free flow cross section of the hydraulic lines (32) and of the connections on the piston side (31) of the hydraulic cylinder (19) is greater than on the piston-rod side (34) of the hydraulic cylinder (19).
 10. Piston press according to claim 5, characterized in that the temperature of the hydraulic fluid can be regulated in such a way that the temperature of the hydraulic fluid approximately maintains a predefined value.
 11. Piston press for pressing liquids out of laundry (11) comprising a press frame (17) which has a base (12) and a press ram (18) which can be moved up and down, and a press basket (23) for holding the laundry (11), characterized in that the base (12) has at least one storage container for the liquid pressed out of the laundry (11).
 12. Piston press according to claim 11, characterized in that the volume of the at least one storage container (36) is dimensioned to be larger than the maximum amount of liquid which accumulates as the laundry (11) is pressed in the press basket (23).
 13. Piston press according to claim 12, characterized in that the at least one storage container has a volume which is at least suitable to accommodate twice the quantity of liquid which accumulates as the laundry (11) is pressed in the press basket (23).
 14. Piston press according to claim 11, characterized in that each storage container (36) is formed by constructing the base (12) as a frame tank (35).
 15. Piston press according to claim 14, characterized in that an upper side of the base (12) is formed by a top wall (13) of the frame tank (35) which, at least in the region of the press basket (23), has drainage holes (14).
 16. Piston press according to claim 15, characterized in that at least part of the storage container (36) is arranged in the region under the drainage holes (14).
 17. Piston press for pressing liquids out of laundry (11) comprising a press frame (17) which has a base (12) and a press ram (18) which can be moved up and down, and a press basket (23) for holding the laundry (11), characterized in that at least one analogue distance measuring device is assigned to the press frame (17) to determine the position of at least the press ram (18).
 18. Piston press according to claim 17, characterized in that a further analogue distance measuring device is provided, by means of which the position of the press basket (23) can be determined.
 19. Piston press according to claim 17, characterized in that the respective distance measuring device is assigned to a press yoke (16) of the press frame (17).
 20. Piston press according to claim 17, characterized in that the respective distance measuring device is designed as an acoustic distance sensor.
 21. Piston press according to claim 20, characterized in that the ram plate (21) of the press ram (18) is assigned at least one reflector for the ultrasound waves from the acoustic distance sensor.
 22. Piston press according to claim 20, characterized in that the press basket (23) is assigned at least one reflector for the ultrasound waves from the acoustic distance sensor.
 23. Piston press according to claim 20, characterized in that the acoustic distance sensor is an ultrasound sensor (40). 